Shell-structured particles for sunscreen applications

ABSTRACT

Shell-structured particles for sunscreen applications are provided herein. A composition includes one or more zinc oxide particles constituting a core material in a sunscreen composition, one or more particles coating the one or more zinc oxide particles, wherein each of the one or more particles comprises a band gap within a predetermined range, and wherein said one or more particles are selected based on a desired absorption spectrum of the sunscreen composition, and an anti-reflective coating applied to the surface of the one or more particles coating the one or more zinc oxide particles.

FIELD

The present application generally relates to chemical technology, and, more particularly, to sunscreen technologies.

BACKGROUND

Sunscreen creams and other such compositions are commonly used to prevent ultraviolet (UV) radiation (also referred to herein as “light” in this context) from reaching the skin of a human user and causing damage. It is noted that UV light is an electromagnetic radiation with a wavelength range between approximately 280 nanometers (nm) and approximately 400 nanometers (specifically, that is the range of UV radiation that is not absorbed by the ozone).

A common active ingredient of existing sunscreen compositions is zinc oxide (ZnO). ZnO is a semiconductor that has a specific band gap, and particles of ZnO used in existing sunscreen compositions are typically approximately 50-300 nm in size. Additionally, in existing sunscreen compositions, typical ZnO materials are capable of absorbing UV light (that is, blocking the UV light from passing through the sunscreen composition to be absorbed by the skin of the user) within a wavelength range of approximately 290 nm through only approximately 350-380 nm.

Additionally, high sun protection factor (SPF) sunscreen compositions, which can absorb a large majority of the UV light in the range of 290-380 nm, require the addition of a higher density of ZnO particles, which causes the composition to become white and/or opaque due to light scattering from the ZnO particles, and which is an often undesirable property to consumers.

SUMMARY

In one embodiment of the present invention, oxide-based nanoparticles for use in sunscreen applications are provided. An exemplary method can include selecting one or more particles to serve as a core material in a sunscreen composition, wherein each of the one or more particles comprises a band gap within a predetermined range, and wherein said selecting is based on a desired absorption spectrum of the sunscreen composition; coating the one or more particles with at least one layer of zinc oxide.

In another embodiment of the invention, a sunscreen composition can include one or more particles constituting a core material in a sunscreen composition, wherein each of the one or more particles comprises a band gap within a predetermined range, and wherein said one or more particles are selected based on a desired absorption spectrum of the sunscreen composition; at least one layer of zinc oxide particles coating the one or more selected particles; and an anti-reflective coating applied to the surface of the one or more particles coating the one or more zinc oxide particles.

Additionally, in one embodiment of the present invention, an exemplary method can include selecting one or more particles to serve as a coating layer in a sunscreen composition, wherein each of the one or more particles comprises a band gap within a predetermined range, and wherein said selecting is based on a desired absorption spectrum of the sunscreen composition; and coating one or more zinc oxide particles with the one or more selected particles.

In yet another embodiment of the invention, a sunscreen composition can include one or more zinc oxide particles constituting a core material in a sunscreen composition; and one or more particles coating the one or more zinc oxide particles, wherein each of the one or more particles comprises a band gap within a predetermined range, and wherein said one or more particles are selected based on a desired absorption spectrum of the sunscreen composition.

These and other objects, features and advantages of the present invention will become apparent from the following detailed description of illustrative embodiments thereof, which is to be read in connection with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a diagram illustrating a core-shell structure, according to an exemplary embodiment of the invention;

FIG. 1B is a diagram illustrating a core-shell structure with an anti-reflective coating (ARC), according to an exemplary embodiment of the invention;

FIG. 2A is a diagram illustrating a core-shell structure, according to an exemplary embodiment of the invention;

FIG. 2B is a diagram illustrating a core-shell structure with an ARC, according to an exemplary embodiment of the invention;

FIG. 3 is a flow diagram illustrating techniques according to an embodiment of the invention; and

FIG. 4 is a flow diagram illustrating techniques according to an embodiment of the invention.

DETAILED DESCRIPTION

As described herein, an embodiment of the present invention includes shell-structured particles for sunscreen applications. As further detailed herein, one or more embodiments of the invention include generating compositions and methods of use thereof for effectively blocking more and/or all of the complete spectrum of UV light (that is, as noted above, the UV radiation that is not absorbed by the ozone, and which ranges between approximately 280 nm and 400 nm) while also preventing whitening effects caused by the scattering of light in the visible spectrum (that is, radiation between approximately 400 nm and 700 nm).

At least one embodiment of the invention includes introducing a copper oxide (Cu₂O) particle or coating layer to form a ZnO—Cu₂O or Cu₂O—ZnO core-shell structure particle for use in sunscreen compositions. As detailed herein, utilization of Cu₂O (and/or analogous materials) can provide extended optical absorption (for sunscreen compositions) of wavelengths of light up to approximately 500 nm. The degree and/or the range of such extended absorption can be controlled by the size of the Cu₂O particle, the thickness of the Cu₂O coating, and/or the volume ratio between ZnO and Cu₂O.

As noted, in at least one embodiment of the invention, the Cu₂O material can be replaced with one or more other materials having a band gap of approximately 2-3 electron volts (eV), such as, for example, zinc oxy-sulfide (ZnOS), ZnO_(x)S_(1-x), wherein 0≤x≤1, indium sulfide (In₂S₃), indium oxy-sulfide (In₂(O_(x)S_(y1-x))₃, wherein 0≤x≤1, or combinations thereof. Such materials can be utilized, alone or in combination, to tune the absorption spectrum of the sunscreen composition.

In one or more embodiments of the invention, the core portion of a core-shell structure can include a single particle or multiple particles. Additionally, in at least one embodiment of the invention, the surface of the core-shell structure can be roughened to provide reduced optical reflection.

Further, as detailed herein, one or more embodiments of the invention can include applying an ARC to the outside and/or exterior surface of the core-shell particles to minimize reflection from the particles. In such an embodiment, the ARC can include any material having a refractive index between that of ZnO (or Cu₂O) and air (or surrounding media), which allows light to better couple into the core-shell particle structure and limits and/or prevents scattering at the ZnO (Cu₂O) interface. Such materials can include, for example, silicon dioxide (SiO₂), magnesium fluoride (MgF₂), fluoropolymers, etc.

Additionally, in such an embodiment, the ARC can include a single layer or can be comprised of multiple layers, wherein the refractive index of the layers are graded between that of the ZnO (or Cu₂O) and that of the surrounding media (such as air). Further, an ARC utilized in one or more embodiments of the invention can be dense or porous, wherein porous layers can contain an effective refractive index between that of air and that of the coating and/or shell material. Additionally, an ARC utilized in one or more embodiments of the invention can be smooth or roughened, wherein roughened layers can contain an effective refractive index between that of air and that of the coating and/or shell material.

FIG. 1A is a diagram illustrating a core-shell structure, according to an exemplary embodiment of the invention. Specifically, FIG. 1A depicts a Cu₂O core 102 coated by a ZnO shell 104. Additionally, FIG. 1B is a diagram illustrating a core-shell structure with an ARC, according to an exemplary embodiment of the invention. Specifically, FIG. 1B depicts a Cu₂O core 102 coated by a ZnO shell 104, and the core-shell structure further coated by an ARC layer 106 (such as, for example, SiO₂).

FIG. 2A is a diagram illustrating a core-shell structure, according to an exemplary embodiment of the invention. Specifically, FIG. 2A depicts a ZnO core 104 coated by a Cu₂O shell 102. Additionally, FIG. 2B is a diagram illustrating a core-shell structure with an ARC, according to an exemplary embodiment of the invention. Specifically, FIG. 2B depicts a ZnO core 104 coated by a Cu₂O shell 102, and the core-shell structure further coated by an ARC layer 106 (such as, for example, SiO₂).

FIG. 3 is a flow diagram illustrating techniques, according to an embodiment of the present invention. Step 302 includes selecting one or more particles to serve as a core material in a sunscreen composition, wherein each of the one or more particles comprises a band gap within a predetermined range (for example, between approximately two and three eV), and wherein said selecting is based on a desired absorption spectrum of the sunscreen composition. The one or more particles can include one or more copper oxide particles. Step 304 includes coating the one or more particles with at least one layer of zinc oxide.

The techniques depicted in FIG. 3 can also include adjusting the desired absorption spectrum of the sunscreen composition by adjusting the size of the one or more selected particles, adjusting the thickness of the at least one layer of zinc oxide coating the one or more particles, and/or adjusting the volume ratio between the one or more particles and the at least one layer of zinc oxide.

Additionally, the techniques depicted in FIG. 3 can include manipulating the surface of the at least one layer of zinc oxide coating the one or more particles to form a roughened surface. Further, at least one embodiment of the invention can include applying an anti-reflective coating to the surface of the at least one layer of zinc oxide, wherein the anti-reflective coating comprises a material having a refractive index within a predetermined range.

Also, an additional embodiment of the invention includes a composition that includes one or more particles constituting a core material in a sunscreen composition, wherein each of the one or more particles comprises a band gap within a predetermined range, and wherein said one or more particles are selected based on a desired absorption spectrum of the sunscreen composition; and at least one layer of zinc oxide particles coating the one or more selected particles. Such a composition can also optionally include an anti-reflective coating applied to the surface of the at least one layer of zinc oxide, wherein the anti-reflective coating comprises a material having a refractive index within a predetermined range.

FIG. 4 is a flow diagram illustrating techniques, according to an embodiment of the present invention. Step 402 includes selecting one or more particles to serve as a coating layer in a sunscreen composition, wherein each of the one or more particles comprises a band gap within a predetermined range (for example, between approximately two and three eV), and wherein said selecting is based on a desired absorption spectrum of the sunscreen composition. The one or more selected particles can include one or more copper oxide particles. Step 404 includes coating one or more zinc oxide particles with the one or more selected particles.

The techniques depicted in FIG. 4 can also include adjusting the desired absorption spectrum of the sunscreen composition by adjusting the size of the one or more selected particles, adjusting the thickness of the one or more particles coating the one or more zinc oxide particles, and/or adjusting the volume ratio between the one or more selected particles and the one or more zinc oxide particles.

Additionally, the techniques depicted in FIG. 4 can include manipulating the surface of the one or more particles coating the one or more zinc oxide particles to form a roughened surface. Further, at least one embodiment of the invention can include applying an anti-reflective coating to the surface of the one or more particles coating the one or more zinc oxide particles, wherein the anti-reflective coating comprises a material having a refractive index within a predetermined range.

Further, yet another embodiment of the invention includes a composition that includes one or more zinc oxide particles constituting a core material in a sunscreen composition; and one or more particles coating the one or more zinc oxide particles, wherein each of the one or more particles comprises a band gap within a predetermined range, and wherein said one or more particles are selected based on a desired absorption spectrum of the sunscreen composition. Such a composition can also include an anti-reflective coating applied to the surface of the one or more particles coating the one or more zinc oxide particles, wherein the anti-reflective coating comprises a material having a refractive index within a predetermined range.

The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used herein, the singular forms “a,” “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “comprises” and/or “comprising,” when used in this specification, specify the presence of stated features, steps, operations, elements, and/or components, but do not preclude the presence or addition of another feature, step, operation, element, component, and/or group thereof.

At least one embodiment of the present invention may provide a beneficial effect such as, for example, generating extended optical absorption of wavelengths of light up to approximately 500 nm.

The descriptions of the various embodiments of the present invention have been presented for purposes of illustration, but are not intended to be exhaustive or limited to the embodiments disclosed. Many modifications and variations will be apparent to those of ordinary skill in the art without departing from the scope and spirit of the described embodiments. The terminology used herein was chosen to best explain the principles of the embodiments, the practical application or technical improvement over technologies found in the marketplace, or to enable others of ordinary skill in the art to understand the embodiments disclosed herein. 

What is claimed is:
 1. A sunscreen composition comprising: one or more zinc oxide particles; one or more particles coating the one or more zinc oxide particles, wherein the one or more particles comprise a combination of two or more of one or more zinc oxy-sulfide particles, one or more indium sulfide particles, and one or more indium oxy-sulfide particles; and an anti-reflective coating applied to the surface of the one or more particles coating the one or more zinc oxide particles.
 2. The composition of claim 1, wherein the anti-reflective coating comprises silicon dioxide.
 3. The composition of claim 1, wherein the anti-reflective coating comprises multiple layers of the anti-reflective coating.
 4. The composition of claim 1, wherein the one or more particles comprise one or more particles with a roughened surface. 